FIGS. 14 and 15 illustrate the lock-up clutch damper disc disclosed in the U.S. Pat. No. 4,240,532, and FIG. 16 and 17 illustrate an embodiment disclosed in the Japanese patent publication No. 61-28126.
In FIG. 14, a damper disk 100, used as a lock-up clutch disc is disposed between a main part 101 of a torque converter and a front cover 102 welded at a portion 104 to a pump 103 and is connected at an outer peripheral coupling 106 to an input shaft 114. A turbine 107 is connected by rivets 110 to a hub 109 splined onto an output shaft 115. A stator 108 has a one-way clutch 111, of which inner race 112 is splined to a stationary cylindrical shaft 116. The damper disk 110 comprises a clutch plate 117, or piston, axially slidably supported on the hub 109, a drive ring 118 welded to a rear surface of the clutch plate 117, circumferentially extending damper springs 120 disposed in pockets 119 in the drive plate 118, and a driven plate 122 which have claws 121 engaging with the damper springs 120 and fixed to the turbine 107. A friction facing 123 is fixed to a front surface of the clutch plate 117.
When the facing 123 on the clutch plate 117 is pressed onto the front cover 102 by a difference between pressures at the opposite sides of the clutch plate 117, the front cover 102 is connected to the turbine 107 through the damper disk 100.
As shown in FIG. 15, the drive plate 118 has outer rims 125 and inner support walls 126, for forming the spring pockets 119 therebetween, as well as projections 127 and 128 which form spring receivers or spring supports at opposite sides of the spring pockets 119. Each spring pocket 119 accommodates a set of one long damper spring 120 and one short damper spring 120a. The claws 121 are disposed between adjacent springs 120 and 120a.
There are following disadvantages in the structures disclosed in the U.S. Pat. No. 4,240,532.
In the assembling operation, each pair of the springs 120 and 120 must be held apart in each pocket 119 so as to insert the claw 121 therebetween. This operation is laborious and it is difficult to check the correct relationship between the springs and claws during the assembling.
In a high speed driving, a strong centrifugal force is applied from the springs to the outer rims 25. However, when the clutch is engaging or disengaging, i.e., when the clutch plate axially moves, the springs 120 and 120a directly engaging the claws 121 tend to axially move together with the claws 121 with respect to the drive plate 118. Therefore, a large friction is caused between the springs 120 and 120a and the outer rims 125, which prevents the smooth movement of the clutch plate, and thus, the smooth operation of the clutch.
Since the centrifugal force of the springs 120 and 120a is directly applied to the outer rims 125, the outer rims 125 must be made of a thick plate. As shown in FIG. 14, because the drive plate 118 has a thickness nearly the same as that of the clutch plate 117, the spring pockets are axially narrow so that it may be impossible to dispose damper springs having a large diameter therein, even when the large springs are desirable for achieving effective damping function. Further, the thick plate causes increase in the weight, which deteriorates the response of the clutch. The thick plate also causes increase in cost.
In order to avoid the above disadvantages, such structures may be employed, as shown in FIG. 14a, in which end portions of the drive plate 118 fixed to the clutch plate 117 are radially inwardly curved to form stoppers 125a for preventing axial movement of the damper springs 120. These inclined stoppers 125a increase the strength of the rims 125 so that the thickness of the plate can be reduced to some extent. However, because the the centrifugal force of the damper springs 120 is supported only by the drive plate 118, it is impossible to sufficiently reduce the thickness of the plate.
In the device shown in FIGS. 16, and 17, the clutch plate 117 is integrally provided with outer rims 117a which directly support the damper springs 120. Spring supports 130 which support the ends of the damper springs 120 is riveted to the clutch plate 117. The spring supports 130 include support walls 131. Spring seats 132 (FIG. 17) is associated to the springs.
There is however following disadvantages in the device shown in FIGS. 16 and 17.
Because it is necessary to use a thick plate for the clutch plate 117 for preventing deformation of the outer rims 117a to which the centrifugal force of the damper springs 120 are applied, the material cost thereof is high.
Since the damper springs are radially and axially supported by the cylindrical surfaces of the rims 117a and the radial surface of the clutch plate 117, respectively, it is necessary to increase the hardness of the surfaces for preventing the wear thereof. However, heat treatment for the hardening causes deformation of the clutch plate 117, so that it is necessary to polish it for maintaining a high flatness of the facing 123, resulting in a high manufacturing cost.
Since a plurality of spring supports 130 are used, the assembling is laborious and the precision in sizes may deteriorate.
Accordingly, it is an object of the invention to provide a damper disk overcoming the above-noted disadvantages.